The present invention relates to a plate winding apparatus wherein both end portions of a printing plate wound around the circumferential surface of a plate cylinder in a rotary press are held by a winding rod arranged in a first groove having a circular section in a circumferential portion of the plate cylinder, the winding rod is pivoted to wind both end portions of the plate into the first groove, and the plate is brought into tight contact with the circumferential surface of the plate cylinder.
A conventional plate winding apparatus of this type is disclosed in Japanese Utility Model Laid-Open No. 60-12441. That is, a first groove having a substantially circular section is formed in a circumferential portion of a plate cylinder by its entire length in the axial direction of the plate cylinder. The plate winding apparatus is disposed in the circumferential portion of the plate cylinder. A winding rod having a circular section is pivotally fitted in the first groove so that one end extends from a cylinder end face. A groove extending in the longitudinal direction of the winding rod is formed in its circumferential surface. A compression coil spring is inserted between the cylinder end face and a lever fixed to a portion of the winding rod extending from the plate cylinder end face.
A printing plate to be mounted on this plate cylinder has a rectangular shape made of an aluminum plate or the like, and its leading-side end portion is acutely bent by a plate bending machine or the like. The trailing-side end portion of the plate is bent at an almost right angle.
With the above structure, when a plate is to be wound around the circumferential surface of the plate cylinder, the leading-side bent end portion of the plate is inserted into a first groove between the winding rod and an inner wall surface of the first groove of the plate cylinder, and the plate is wound around the circumferential surface of the plate cylinder. The trailing-side bent end portion of the plate is inserted into the groove of the winding rod. At this time, the winding rod receives a pivotal force by an elastic force of the compression coil spring through a lever in a plate tightening direction. A pivotal limit position of the winding rod is defined by a stopper. In this state, when the winding rod is pivoted, the leading-side bent end portion of the plate is clamped between the winding rod and the inner wall surface of the first groove. The trailing-side bent end portion is wound together with the winding rod since this end portion is inserted into the groove of the winding rod. Therefore, the plate is tightened to be brought into tight contact with the circumferential surface of the plate cylinder. The lever passes over its dead center during pivotal movement. At the end of the pivotal movement, the elastic force of the compression coil spring acts on the plate in the plate tightening direction.
In the conventional plate winding apparatus having the above arrangement, however, since the winding rod is tightly fitted in the first groove of the circular section and cannot be moved within the first groove upon pivotal movement of the winding rod, when a plate thickness is changed, the distance between the inner wall of the first groove and the winding rod which receives the leading-side bent end portion of the plate cannot be adjusted to cope with a change in plate thickness. When the thickness of the plate is large, after the trailing-end bent edge of the plate is brought into contact with the leading-side bent end portion of the plate, the trailing-side bent edge and the trailing-side flat surface of the plate are brought into sliding contact with the leading-side bent portion upon pivotal movement of the winding rod, both the leading- and trailing-side bent portions are undesirably damaged, and the plate cannot be reused, resulting in inconvenience. In addition, since the compression coil spring for biasing the winding rod in the plate tightening direction is arranged on one side of the plate cylinder, a plate tightening force acting on the entire surface of the plate cylinder is locally nonuniform. As a result, misalignment of the plate tends to occur.